The current invention is directed to ball valve assemblies that are configured to prevent leakage of liquids from within mobile tanks or other large tank-like containers. More particularly, but not exclusively, the current invention is directed to a ball valve assembly configured to prevent leakage of liquid commodities from railroad tank cars. Railroad tank cars that ship liquid commodities are generally divided into two categories: low pressure (general purpose) and (ii) high pressure tank cars. The present invention addresses general purpose tanks as (i) railroad cars that transfer these commodities from the tank cars (ii) through a valve located at the bottom center position of the tank [′bottom outlet valve′]. These prior existing valves contain a variety of structures such as, but not exclusively, plug, butterfly or ball valves. The most common prototype is the ball valve, and most particularly this invention pertains to the ball valve variety.
Current ball valve design does not solve the problem of contamination of the commodity liquid. Contaminants such as, but not exclusively, tank scale, dirt and debris at the bottom of a typical commodity tank, abrade the valve ball component and thereby result in leakage. These current ball valves also do not solve the problem of corrosion of ball valve assembly components. Abrasive materials embed in (i) the valve seat and (ii) score valve ball components generally made of stainless steel. For example, scratching as well as other abrasive or corrosion damage to a conventional metal ball component creates small channels that inevitably cause leakage of the liquid commodity even when the ball valve assembly is ostensibly closed. To solve this problem, the current invention implements valve seats and valve balls generally made of a ceramic material, and more particularly a specific ceramic material. Ceramics are much harder materials than steel and not easily abraded by contaminants. They are also very resistant to corrosion by chemical liquid commodities carried in the tanks.
Midland currently produces bottom outlet ball valve Model No. 522 for railroad tank cars. Midland's valve contains (i) seats made of Teflon®/flouropolymer [TFE] or thermoplastic materials. Jamesbury produces a bottom outlet ball valve with a polytetrafluorocarbon [hereinafter ‘PTFE’] valve seat for an effective seal between the ball component and the seat. Ball components are generally comprised of metal, particularly stainless steel, in the ball valve assembly industry. Unfortunately, TFE and PTFE seats are particularly susceptible to contaminants that embed in the seats and score the steel ball components.
To solve this problem the current invention implements a component designated as a ceramic wiper, and this ceramic wiper forms a rigid annular ring. When this ceramic wiper is combined with a ball component made of a ceramic material this wiper (i) substantially reduces scoring and corrosion of the ball component and (ii) prevents contaminants from accessing and embedding in the seats. The ceramic wiper is combined with a ceramic ball component to reduce abrasion of both these components. In sum, the current invention solves the industry leakage and corrosion problems with (i) the sealing capability of a soft valve seat and (ii) the durability of ceramic components.
In previously existing devices of this particular industry, TFE and PTFE are the most widely used material for ball assembly valve seats because of their cost efficiency. Polyether ether ketone [hereinafter PEEK] has excellent mechanical and chemical resistance at higher temperatures than PTFE. PEEK costs at least twice as much as PTFE, while the ceramic material in the current invention is more costly than PTFE but not cost prohibitive. The most preferred ceramic material for the current invention is zirconium oxide with preferably (i) tensile strength of 70-85 kpsi and (ii) thermal expansion coefficient of 5.9e-06 per degree Celsius. However, materials such as aluminum oxide compounds or silicon nitride are also satisfactory.
The current invention also solves the problem of handles which (i) pre-attach to a ball valve assembly and (ii) thereafter inadvertently swing open during transport of a liquid commodity. In the current art, whenever a tank car derails often the pre-attached valve assembly handle does not predictably shear and fall from the ball valve assembly; instead the protruding handle remains intact and attached to the bottom outlive valve at the railroad tank car bottommost surface. When the intact handle inadvertently swings opens during derailment, (i) the valve assembly automatically opens and (ii) the liquid commodity pours from the tank car with financial, business, and environmental consequences.
For example, Midland's bottom outlet ball valve comprises a large long handle that significantly protrudes from the valve assembly. www.midlandmfg.com/products/general-purpose-car/ball-valves on Apr. 8, 2013. In a similar manner Jamesbury, Inc. discloses a ball valve with a standard attached handle. See http://www.valvesandinstruments.com/jamesbury-ball-valves. Both Midland and Jamesbury valve assemblies contains stems with male ends that solely and exclusively accommodate proprietary handles. Consequently ball valve assembly handles are not interchangeable with each other or other commercially available rotating operating devices. To solve this problem the design of the current invention contains a drive coupling to which conventional square drive tools can each operatively attach to the ball valve assembly.
In sum, the current invention solves the handle problem by insertion of the new drive coupling so loading personnel may implement a ubiquitous square drive tool to operate the ball valve assembly. In addition to this safety improvement, there is no additional sunk cost to implement and retrofit this drive coupling, because square drive tools are available at on loading and offloading railroad facilities. Furthermore, pending United States Department of Transportation regulations will require that all permanently affixed tools/handles be removed from bottom outlet valves. Consequently, the drive coupling of the current invention adaptor will solve the urgent need for compliance with these pending regulations.
A third advantage of the current invention is the stem packing assembly. The stem packing assembly provides a seal between (i) a rotating stem and (ii) the stationary valve assembly body. Currently available stem packing assemblies comprise many forms such as woven graphite material, woven TFE rope and numerous TFE chevron rings. These components insert into a stem longitudinal stem cavity between the rotating stem and valve assembly body. As the stem packing is increasingly compressed, the chevron rings (i) flare outward and (ii) thereby initially seal and contact the cylindrical wall of the longitudinal stem cavity and stem exterior wall surface.
In these prior existing stem packing assemblies, the stem packing is mechanically compressed when the ball valve assembly is initially assembled. This initial compression deflects the conventionally placed Bellville washers or wave washers whenever the ball valve assembly is initially installed within a tank car. However, there is a long-felt need to prolong the effective working life of the stem packing assembly: With long-term operation thereafter, this same stem packing with the currently available stem packing and spacers wears and inevitably creeps (by cold flow) away from the stem exterior surface. This process eventually reduces the effectiveness of the stem packing to seal between the stem and the valve body inner surface. Consequently, because of the rotating stem, wear of the stem packing requires progressive compression against the stem longitudinal cavity as time progresses.
The current solution to this problem is not sufficient to prevent leakage from the stem longitudinal cavity over time and rail car movement. For example, many manufacturers currently include chevron PTFE rings as (i) part of the ball valve assembly (ii) that is currently compressed by two spring loaded nuts with numerous supplementary components. For example a Jamesbury valve comprises an indicator stop, reinforcing ring, compression ring, compression plate, disc spring and flat washer in addition to several chevron rings. In this previously existing device, an applied force collectively compresses the compression plate and these numerous rings against the stem packing. In contrast, in the current invention, a single stem lock nut and an appropriate wave spring is threaded upon the stem. Single stem lock nut thereby forces a wave spring, stop indicator plate and packing spacer against the stem packing.
In this manner the current invention (i) reduces the number of stem assembly components from twelve components of the Jamesbury ball valve to two components (ii) by implementing a single spring loaded nut. In contrast, the Midland ball valve assembly implements a single locknut to seal a stem packing against the stem during manufacture. However in this prior art device there is no additional compression device to compensate for stem packing (i) cold flow and (ii) deterioration after this initial assembly and during subsequent movement of the tank during (iii) large temperature discrepancies.
The Jamesbury ball valve assembly implements a compression plate and several ring devices to compress the stem packing to the stem shaft. In particular, the Jamesbury valve also requires a first and second series of Bellville washers for additional compression. In contrast, in the current invention the stem packing is compressed along the stem by a single wave spring during initial manufacture process: This initial setting by the manufacturer conventionally applies 150 foot-pounds of torque to the stem lock nut. Thereafter the ball valve assembly is installed within the bottom surface of a tank car. The single wave spring provides sufficient additional compression of the stem packing during time and wear than conventional springs and previously existing stem packing assemblies.
Because of the rotating shaft, wear on the stem packing requires additional compression of the stem packing against the stem and the interior surface of the stem block as time progresses. Otherwise the stem packing will deteriorate within the stem bore and recede from the stem and the interior stem block surface, thereby reducing the sealing ability of the stem packing. Without additional spring force compressing the stem packing, the ball valve assembly is more susceptible to leakage along the valve stem longitudinal length over time. The current invention solves this problem with a single wave spring that (i) continuously compresses the stem packing to the stem and (ii) slows the wear of the stem packing. In the current invention, a single stem lock nut is also threaded upon the stem and constrained within the valve body.
This single stem lock nut forces the wave spring and packing spacer against the stem packing. Consequently the current invention comprises a new subassembly that includes the stem packing chevron rings, a single lock nut and a single wave spring for (i) reduction of stem packing components as well as (ii) an increased operating life of the stem packing materials. During its useful service period the stem packing wears and thereafter conforms to the annular cavity between the stem bore and the stem shaft, thereby reducing the sealing ability of the stem packing Without additional spring force compressing the stem packing, the ball valve assembly is more susceptible to leakage along the valve stem longitudinal length. In sum, the stem packing assembly is a significant improvement because the presence of a single compression nut significantly reduces the number of necessary ball valve assembly components.
Consequently the current invention (i) reduces the number of packing components from twelve components of the Jamesbury ball valve to two components (ii) by implementing a single spring loaded nut along with the wave spring. The Midland ball valve assembly implements a single locknut to seal a stem packing against the stem; however, there is no additional compression device after this initial setting. The Jamesbury ball valve assembly implements a compression plate and several ring devices to compress the stem packing to the stem shaft. In particular, the Jamesbury prototype also requires a first and second series of Belville washers for additional compression. In sum, the stem packing assembly is a significant improvement because the presence of a single compression nut significantly reduces the number of necessary ball valve assembly components.
There are a variety of tank car bottom outlet flange configurations. However the majority of configurations contain (i) a six inch to eight inch orifice (ii) with eight tapped openings along a bolt circle with a diameter of approximately ten and five-eight inches. The flange sealing joint is either (i) an O-ring held within a groove or (ii) a tongue and groove with a gasket. The preferred sealing component is a tongue and groove application for the current invention. The ball valve assembly of the current invention and the Midland ball valve assembly need not be removed from the tank to replace or inspect the internal ball valve assembly components. However the Jamesbury valve assembly has an insert item on the top of the ball valve assembly by which the internal components are physically accessed only if the ball valve assembly is removed from the tank.